While it would prevent limited cases of less-than-ideal curation, I don't believe this would be a net positive. More people would lose out in both post rewards and curation rewards than Hive would gain from limiting intentionally-late curation.

I often find myself voting on posts 2-5 days old because I can't see everything as it comes out. I would be less likely to vote on those posts if there were a severe curation penalty. And those people posting would lose out on my vote and any other late-comers' votes.

Furthermore, this would incentivize bot voting even more.

Less-than-ideal curators are easier to spot and counter than shaking up the curation system to this degree.